WASHINGTON — One thing is clear about John McCain's foreign policy views: Much like his political heroes Ronald Reagan and Theodore Roosevelt, he believes that America's power is a force to make the world better.

How McCain would wield that power as president is less clear, however.

The Arizona senator, now the presumptive Republican presidential nominee, is a leading supporter of President Bush's troop "surge" in Iraq — a stance that some observers credit with reviving his political fortunes as security in Iraq has improved, at least temporarily.

Less well known are McCain's promises, if elected, to expand the Army and the Marine Corps to 900,000 soldiers and Marines from a planned strength of about 750,000; to form a U.S.-led League of Democracies to act when the United Nations can't or won't; and to form a new government unit, patterned after the World War II-era Office of Strategic Services, "to fight terrorist subversion" and "take risks that our bureaucracies today rarely consider taking."

McCain's foreign-policy advisers are a mix of traditional Republican "realists," who favor a pragmatic approach to the world, and "neoconservatives," who lobbied for the Iraq invasion, advocate tougher action to squelch Iran's and North Korea's nuclear weapons ambitions and favor using U.S. power to transform the Muslim world.

McCain has broken with his party on some key issues. He's taken a more lenient stance on immigration, expressed greater concern about global climate change and opposed the Bush White House on the Guantanamo Bay prison and the use of interrogation techniques that could be considered torture.

"I think he's a very interesting mix," said Gary Samore, who served in the Clinton White House and is now vice president of the nonpartisan Council on Foreign Relations.

On issues such as climate change and immigration, McCain would be "very different from the Bush administration," Samore said. "On other issues, he's been very bellicose," he added, citing Iran and North Korea.

McCain already has indicated that he plans to use national security as a cudgel against the eventual Democratic nominee in the general election campaign.

In Norfolk, Va., earlier this month, he talked tough on Iran and said he's the best prepared candidate to deal with security threats on his first day in office.

Democratic candidates Sens. Hillary Clinton and Barack Obama "want to set a date for withdrawal in Iraq. I believe that would have catastrophic consequences. They (attackers) would try to follow us home," McCain said.

But McCain hasn't spelled out in detail how he'd deal with threats to America's security.

His advisers dispute the notion that McCain, a former Navy pilot who was a prisoner of war in North Vietnam, would be quick to order the U.S. military into action.

McCain is willing to "use military force when necessary as a last resort," said Randy Scheunemann, the campaign's director of foreign policy and national security. But the senator also believes the war on terrorism "is a war of ideas," he said.

McCain's foreign-policy team is sprinkled with people, including Scheunemann, who were ardent backers of the 2003 Iraq invasion and who dismissed critics who warned of unintended consequences. They include former CIA director James Woolsey, an adviser mostly on energy security, and William Kristol, the editor of the conservative Weekly Standard.

But McCain's views on the use of U.S. military power have shifted over time.

As a freshman GOP congressman in 1983, he drew national media attention for opposing President Ronald Reagan's extension of the Marine deployment in Lebanon.

He said in a speech on the House of Representatives floor: "The longer we stay in Lebanon, the harder it will be for us to leave. We will be trapped by the case we make for having our troops there in the first place."

But in the past dozen years, McCain has supported U.S. interventions in Bosnia, Kosovo, the 1991 Gulf War and Iraq.

Samore said that, whatever McCain's instincts, he'll be restrained from new interventions by the wars in Iraq and Afghanistan. "Bush has overdrawn the bank account on use of force for the time being," he said.